1. Field of the Invention
The present invention relates to chromatographic analyzers. More specifically, the present invention is directed to a sample injection apparatus for a chromatographic analyzer.
2. Description of the Prior Art
The use of chromatographic analyzers for analyzing fluid samples, e.g., gas mixtures, is well-known in the art. A sample injection means is used for selectively injecting a sample of the gas to be analyzed into a carrier fluid stream to be carried to the chromatographic separating column. The purpose of the sample injector is two-fold, i.e., it must inject a sample into the carrier fluid stream and it must provide a means for predetermining the volume of the sample to be injected. The prior art sample injection devices have included mechanically operated syringes, e.g., U.S. Pat. Nos. 3,940,995 and 3,985,166, valves having internal storage loops, e.g., U.S. Pat. Nos. 3,787,026 and 3,975,946 and other complicated mechanical devices which have usually been unable to provide long term reliability in combination with a low manufacturing cost. Accordingly, it would be desirable to provide a sample injection apparatus capable of having extremely long operating life as well as a simple and inexpensive structure.